The invention concerns an expandable and contractible coiler mandrel, especially for coiling a metal strip, which has: a rotatably supported coiler mandrel shaft, which has at least one wedge surface on its outer circumference; a number of cooperating segments, which have a coiling surface, especially for the metal strip, on their outer circumference, and which have at least one opposing wedge surface that cooperates with the wedge surface of the coiler mandrel shaft in their end region facing away from the coiling surface; means for shifting the segments relative to the axial direction of the coiler mandrel shaft; and a supply system with which a lubricant, especially lubricating grease, is conveyed to places in the coiler mandrel that require lubrication.
Coiler mandrels of this type are needed, for example, in the production of steel strip. The strip is coiled or uncoiled on them, for example, to carry out further processing steps on the strip. To allow the strip to be coiled or uncoiled on the mandrel without slipping, the coiler mandrel can be expanded and contracted. That is, the diameter of the mandrel coiling surface provided for coiling the strip can be varied. In other words, the coiler mandrel is spread, for example, during the coiling operation, to create a nonpositive connection between the mandrel and the metal strip.
In this regard, stable and reproducible operation of the coiler mandrel requires that it be supplied with lubricant, especially lubricating grease. Only then can the operating characteristics of the mandrel be maintained at a constant level over time. In addition, this is the only way to prevent wear.
Various well-known techniques can be used for lubricating the coiler mandrel:
First, the lubrication can be performed manually at predetermined intervals of time by means of grease nipples. A sufficient amount of grease must be applied to last until the next greasing. This can result in overlubrication with unacceptable levels of escaping grease, which is found to be a problem especially because centrifugal action in the coiler mandrel often causes grease loss.
Another possibility for lubricating a coiler mandrel with a free shaft end, usually at the drive end, is lubrication with a rotary distributor from a stationary grease pump. The grease is carried to the coiler mandrel in this way. In this regard, grease can be permanently supplied as part of a central lubrication system, which can be provided especially in the case of a hot coiler.
In the case of coiler mandrels made of high-grade steel, the grease connection is often automatically produced at the service end of the shaft via the mandrel support bearing during a shutdown by means of an attachable medium coupling, and the lubrication is carried out in this way. During the operation of the coiler mandrel, the grease connection is then detached.
Permanently acting lubricant distributors are also known, but they frequently fail to apply the grease pressure necessary to ensure good supply of all lubricating points.
EP 0 722 791 B1 discloses a lubricating device for an expandable coiler mandrel in which all of the lubricating points on the mandrel shaft can be centrally lubricated. In this device, cartridges that communicate with the lubricating points to be supplied with lubricant are inserted in a central bore of the mandrel shaft. In addition, there is a connection to a central grease distributor, which supplies the bores in the cartridge with grease.
DE-OS 20 32 542 also discloses the supplying of lubricant to lubricating points of a coiler mandrel by means of a grease supply system integrated in the mandrel, wherein this system is connected to the feed line of a pressure medium source. The lubricant is fed to the coiler mandrel by a line of this type and a distributor element.
Similar solutions are disclosed by U.S. Pat. Nos. 2,578,953 and 4,213,577.
A disadvantage of the previously known solutions is that too much or too little lubricant is often fed to the coiler mandrel and especially to its lubricating points. In this regard, both insufficient lubrication and excessive lubrication are associated with important disadvantages. In the case of insufficient lubrication, erosion of surfaces that slide on each other in the coiler mandrel can occur. Excessive lubrication not only results in higher costs than necessary, but also can cause environmental pollution, which must then be dealt with at considerable expense.
The stated problem is further intensified by the fact that centrifugal forces in the coiler mandrel can cause the lubricant to be flung away from the point at which it is needed.
In other solutions, handling is associated with significant disadvantages when, specifically, media systems must be attached to the coiler mandrel at certain intervals of time to supply lubricating grease.